Objectives: The TEN(HL) is a clinically-administered test to detect cochlear ‘dead regions’ (i.e. regions of loss of inner hair cell (IHC) connectivity), using a ‘pass/fail’ criterion based on the degree of elevation of a masked threshold in a tone-detection task. With sensorineural hearing loss, some elevation of the masked threshold is commonly observed, but usually insufficient to create a ‘fail’ diagnosis. The experiment reported here investigated whether the gray area between pass and fail contained information that correlated with factors such as age or cumulative high-level noise exposure (> 100 dBA SPL), possibly indicative of damage to cochlear structures other than the more commonly implicated outer hair cells (OHCs).
Design: One hundred and twelve participants (71 female) who underwent audiometric screening for a sensorineural hearing loss, classified as either normal or mild, were recruited. Their age range was 32 to 74 years. They were administered the TEN test at four frequencies, 0.75, 1, 3 and 4 kHz, and at two sensation levels, 12 and 24 dB above their pure-tone absolute threshold at each frequency. The test frequencies were chosen to lie either distinctly away from, or within, the 2 - 6 kHz region where noise-induced hearing loss is first clinically observed as a notch in the audiogram. Cumulative noise exposure was assessed by the Noise Exposure Structured Interview (NESI). Elements of the NESI also permitted participant stratification by music experience.
Results: Across all frequencies and testing levels, a strong correlation was observed between elevation of TEN threshold and absolute threshold. These correlations were little-changed even after noise exposure and music experience were factored out. The correlations were observed even with in the range of ‘normal’ hearing (absolute thresholds ≤ 15 dB HL). Stone et al Supra-threshold losses and TEN test
Conclusions: Using a clinical test, sensorineural hearing deficits were observable even within the range of clinically ‘normal’ hearing. Results from the TEN test residing between ‘pass’ and ‘fail’ reflect decay of processes not related to IHCs. IHC-related processes, for which the TEN test was originally designed, such as may be caused by high-level noise exposure, only dominate when a ‘fail’ criterion is reached.